I think it has something to do with the following settings:

1. Check your Thread Group setup, Same user on each iteration should be ticked

   

2. Check httpclient.reset_state_on_thread_group_iteration property value, if you want to re-use the same connection - you need to set it to false either in user.properties file or via -J command-line argument.

   More information:

   • SSL Configuration
   • Apache JMeter Properties Customization Guide

3. Check your operating system settings with regards to recycling/reusing TCP connections in TIME_WAIT state